Inhibitory effect of resveratrol dimerized derivatives on nitric oxide production in lipopolysaccharide-induced RAW 264.7 cells

Article abstract of DOI:10.1016/j.bmcl.2013.05.058

Four types of resveratrol dimerized analogues were synthesized and evaluated in vitro on LPS-induced NO production in RAW 264.7 cells. The results showed that several compounds, especially those containing 1,2-diphenyl-2,3- dihydro-1H-indene core (type I), exhibited good inhibitory activities. Among 25 analogues, 12b showed a significant inhibitory activity (49% NO production at 10 μM, IC₅₀ = 3.38 μM). Further study revealed that compound 12b could suppress LPS-induced iNOS expression, NO production, and IL-1β release in a concentration-dependently manner. The mechanism of action (MOA) involved for its anti-inflammatory responses was through signaling pathways of p38 MAPK and JNK1/2, but not ERK1/2.

Full text of DOI:10.1016/j.bmcl.2013.05.058

Bioorganic & Medicinal Chemistry Letters 23 (2013) 4413–4418
Contents lists available at SciVerse ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Inhibitory effect of resveratrol dimerized derivatives on nitric oxide
production in lipopolysaccharide-induced RAW 264.7 cells
Chen Zhong a, , Xin-Hua Liu b, , Jun Chang a, Jian-Ming Yu a, Xun Sun a,
⇑
a Department of Natural Products Chemistry, School of Pharmacy, Fudan University, 826 Zhangheng Road, Shanghai 201203, China
b Department of Pharmacology, School of Pharmacy, Fudan University, 826 Zhangheng Road, Shanghai 201203, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 19 March 2013
Revised 1 May 2013
Accepted 18 May 2013
Available online 28 May 2013
Four types of resveratrol dimerized analogues were synthesized and evaluated in vitro on LPS-induced NO
production in RAW 264.7 cells. The results showed that several compounds, especially those containing
1,2-diphenyl-2,3-dihydro-1H-indene core (type I), exhibited good inhibitory activities. Among 25 ana-
logues, 12b showed a significant inhibitory activity (49% NO production at 10 lM, IC50 = 3.38 lM). Further
study revealed that compound 12b could suppress LPS-induced iNOS expression, NO production, and IL-1b
release in a concentration-dependently manner. The mechanism of action (MOA) involved for its anti-
inflammatory responses was through signaling pathways of p38 MAPK and JNK1/2, but not ERK1/2.
Ó 2013 Elsevier Ltd. All rights reserved.
Keywords:
Resveratrol dimers
Resveratrol analogues
Anti-inflammation
MAPK
Inflammatory reactions take place after injury, infection, or
trauma and induce an accumulation of inflammatory immune
cells. However, prolonged inflammation can be harmful, contribut-
ing to the pathogenesis of many diseases. Inflammatory reactions
are complex and multifactorial condition for which a number of
mediators have been identified.1 Among these, the nitric oxide
(NO) radical generated by phosphorylated endothelial NO synthase
(eNOS) is one of the most important mediators.2 In addition, this
phosphorylation is generated by an inducible enzymes called the
inducible NO synthase (iNOS).3,4 High-output NO by iNOS can pro-
voke deleterious consequences and has been closely correlated
with pathophysiology in a variety of diseases and inflammations.5
Transcriptional induction of iNOS is largely dependent on cooper-
Resveratrol (3,5,40-trihydroxy-trans-stilbene, 1, Fig. 1) is a natu-
ral polyphenol stilbene found in grapes and certain plants used as
medicines. It has been reported to have a diverse range of pharma-
cological properties, including anti-inflammatory action,10 pre-
venting platelet aggregation11 and antioxidant activities.12
Resveratrol can be biotransformed by Botrytis cinerea, a fungal
grapevine pathogen, into resveratrol oligomers such as isopaucifl-
oral F (2a), quadrangularin A (E-3a), parthenocissin A (Z-3a), pall-
idol (4a) and (+)-a
-viniferin (5) (Fig. 1).13,14 Recent findings
suggested that these oligomers also showed a variety of biological
activities. Some of these derivatives demonstrated more potent
biological activities than resveratrol due to their polyphenol mo-
tifs.15 In particular, there were a few reports about anti-inflamma-
tion of resveratrol dimers.15,16
ative activities of multiple transcription factors, including NF-jB
and AP-1 which act important cis-elements for induction of iNOS
Since pallidol was isolated from Caragana sinica and determined
to have estrogen-like activities by our colleagues in their early re-
search,17 we have developed methods to be capable of synthesizing
resveratrol dimers including isopaucifloral F (2a), quadrangularin A
(E-3a), pallidol (4a) and their derivatives.18–20 Some of them have
performed potent neuroprotection activities.21 Recently, Shi and
co-workers reported that resveratrol had the protective function
against various neurological disorders in experimental models,
including brain ischemia, seizures, and neurodegenerative disease
models.22 This work also showed the anti-inflammatory activities
of resveratrol in the brain from both in vivo and in vitro studies
and the relationship between the neuroprotection and anti-inflam-
mation of resveratrol. Thus, it was of interest to screen our previ-
ous synthesized resveratrol dimers and derivatives to verify
whether there is a particularly structural type rendering any
gene transcription.6 Many stimuli, such as lipopolysaccharides
(LPS), can activate the transcription factor NF-jB and phosphoryla-
tion of its upstream signaling pathway mitogen-activated protein
kinase (MAPK).7,8 At present, three major MAPKs have been de-
scribed, which are extracellular signal-regulated kinase (ERK)1/2,
c-Jun N-terminal kinase (JNK)1/2, and p38 MAPK.9 Thus, NO pro-
duction, through iNOS induction by LPS, may reflect the degree
of inflammation and can be one of the tools to assess the effect
of drugs on the inflammatory process.
⇑
Corresponding author. Tel./fax: +86 21 51980003.
E-mail address: sunxunf@shmu.edu.cn (X. Sun).
These authors contributed equally to this work.
0960-894X/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.bmcl.2013.05.058

4414
C. Zhong et al. / Bioorg. Med. Chem. Lett. 23 (2013) 4413–4418
OH
OH
OH
OH
OH
OH
OH
OH
HO
HO
HO
OH
O
OH
OH
1
resveratrol ( )
isopaucifloral F (2a)
quadrangularin A (E-3a)
OH
HO
HO
OH
OH
OH
OH
H
O
H
HO
HO
OH
H
H
H
H
O
H
HO
HO
H
O
OH
HO
OH
3a
)
5
(+)-viniferin ( )
parthenocissin A (Z-
4a
pallidol (
)
Figure 1. Natural resveratrol oligomers.
anti-inflammatory activity. Therefore, three natural products (2a,
E-3a, 4a) and their methylated precursors (6a, 7a, 8a, Fig. 2) were
tested to inhibit LPS induced NO production in RAW 264.7 cells
(Table 1). Interestingly, compound 6a (indenone-type) and 7a (in-
dene-type) showed very good activity in RAW 264.7 cell with 56%
effect on inflammatory reactions mediated through the down-
regulation of the MAPK pathways.25 Therefore, enzyme-linked
immunosorbent assay (ELISA) and Western blot analysis were also
carried out to attempt to identify the mechanisms underlying their
anti-inflammatory effects.
and 61% NO production, respectively at 10
l
M. In addition, meth-
The syntheses of these dimerized derivatives (types I–IV) were
achieved by adopting our previous reported procedures which was
starting from commercially available 3,5-dimethoxybenzoic acid
(9) followed by a sequential process (Scheme 1).18 The synthetic
strategy involved a Wittig–Hornor reaction, Nazarov cyclization,
and Ramberg–Backlund olefination. By incorporating different sub-
stituents on Wittig–Hornor reagents and benzyl mercaptans, total
25 dimerized compounds were synthesized and carefully charac-
terized. Among them, 22 were novel compounds.
The anti-inflammatory activity of 25 compounds against LPS in-
duced NO production in RAW 264.7 cells were evaluated and the
results were shown in Table 1. In general, types I and IV com-
pounds exhibited better inhibitory activity than other two types.
For type I analogues (6a–c), there was no significant difference
when the substituent changed on the ring A (R1 = OMe, H, or F).
All of them (6a–c) showed potent inhibitory activity against LPS
ylated precursors were more effective in the NO production assay
than their corresponding natural products (6a vs 2a, 7a vs E-3a,
and 8a vs 4b).
The preliminary biological data encouraged us to continuously
explore the structure–activity relationships (SARs) of resveratrol
dimerized analogues by modifying the substituent patterns on
the phenyl rings in various scaffolds. It was expected that func-
tional groups on the benzene rings may play a pivotal role in pro-
viding their anti-inflammatory activity.23 In order to make the
discussion clearer, compounds were classified into four types
of structures: type I (6a–c and 12a–c), type II (7a–g), type III
(13a–g), and type IV (14a–g) (Scheme 1). Thus, 25 novel resvera-
trol dimerized derivatives were synthesized24 and evaluated for
inhibition of NO production in LPS-induced RAW 264.7 cells.
Meanwhile, it was reported that resveratrol exerted a regulatory
RO
OR
OR
OR
A
H
H
OR
OR
OR
RO
A
OR
OR
OR
RO
RO
RO
B
OR
O
OR
OR
quadrangularin A (E-3a): R=H
7a : R=Me
pallidol (4a): R=H
8a : R=Me
isopaucifloral F (2a): R=H
6a : R=Me
Figure 2. Natural resveratrol dimers and derivatives synthesized before.

C. Zhong et al. / Bioorg. Med. Chem. Lett. 23 (2013) 4413–4418
4415
Table 1
The effects of novel compounds on LPS induced NO production in RAW 264.7 cells
R1
R1
R1
R1
OMe
OMe
OMe
OMe
OMe
OMe
OMe
OMe
OMe
OMe
*
MeO
*
MeO
S
MeO
*
OMe
R2
OMe
R2
HO
MeO
X
R2
Type I
Type II
7a-g
Type IV
14a-g
Type III
13b-g
6a-c,12a-c
NO production (%)#
IC50 (lM)
a
Entry
Compound
Type
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
2a
3a
4a
6a
6b
6c
7a
7b
7c
7d
7e
7f
7g
8a
12a
12b
12c
13a
13b
13c
13d
13e
13f
13g
14a
14b
14c
14d
14e
14f
14g
I
II
/
I
I
I
II
II
II
II
II
II
II
/
I
I
97.13 0.89
70.00 4.52⁄
89.29 2.23
60.86 5.34⁄
65.95 1.6⁄
57.41 0.25⁄
56.10 2.15⁄
108.44 2.39
84.35 2.04
88.24 0.42
99.24 2.88
95.92 1.62
90.72 0.91
80.16 0.15
58.32 1.22⁄
49.47 2.11⁄
54.01 0.84⁄
70.52 0.87⁄
75.94 0.44
72.40 0.35
78.12 0.17
86.32 0.34
92.48 0.49
79.77 0.48
77.04 2.02
59.48 0.50⁄
67.78 0.92⁄
75.36 1.05
63.46 0.61⁄
81.36 1.06
77.48 1.32
>200
NAb
>200
>200
27.1
44.77
6.26
>200
>200
>200
>200
>200
>200
>200
7.87
3.38
I
NAb
III
III
III
III
III
III
III
IV
IV
IV
IV
IV
IV
IV
12.48
>200
>200
>200
>200
>200
>200
>200
21.59
16.51
>200
26.54
>200
>200
Data shown are means SEM, #P <0.05 compared with control cells (NO production percentage: 13.28 0.19), ⁄P <0.05 compared with LPS-stimulated cells (NO production
percentage: 100 1.46). Data were from at least three independent experiments, each performed in duplicate.
a
IC50 value of each compound was defined as the concentration (lM) of indicated compound that caused 50% inhibition of NO production in LPS-stimulated RAW 264.7
cells.
b
These compounds shows cytotoxic effect at high concentration.
induced NO production (61%, 66%, and 57% NO production at
10 M, respectively). After reduced the carbonyl group of 6b, the
inhibitory activity of the corresponding hydroxyl analogue 12b
was further improved (49% NO production at 10 M,
IC50 = 3.38 M). For types II and III, all analogues exhibited very
for further investigation to identify the mechanism responsible
for it inhibitory effect on RAW 264.7 cells.
l
Initially, the cell viability experiment was performed at
l
5–20
l
M concentration and there was no significantly cytotoxic
M (data not shown). To
l
of 12b at the concentration up to 20
l
weak inhibitory activity, though these analogues in which methox-
yl group on ring A was replace by hydrogen showed slightly better
activity (e.g., 7c in type I and 13b–c in type II). In type IV, the inhib-
itory activity was not increased when methoxyl group was re-
placed by hydrogen on ring B (14d vs 14a). However, 14e, with a
methyl group instead of methoxyl group on ring B did improve
investigate the anti-inflammatory effects of 12b on LPS-induced
inflammatory response, RAW 264.7 cells were first preincubated
with 12b for 2 h, and then stimulated with LPS for 24 h. As illus-
trated in Figure 3A, treatment with LPS (1
crease the expression of iNOS protein; co-treatment with 12b
suppressed LPS-induced iNOS expression in concentration
lg/mL) drastically in-
a
the activity (63% NO production at 10
l
M, IC50 = 26.54
l
M). Inter-
dependent manner. In accordance with this, 12b was reduced
LPS-induced NO production in a concentration dependent manner
(Fig. 3B). A further study revealed that 12b could also inhibit LPS-
induced inflammatory cytokine release. Inflammatory activity for
cytokine IL-1b was measured in LPS-stimulated RAW 264.7 cells
estingly, a most potent compound in this type, 14b, was achieved
when there was no substituent on both ring A and B. Among all the
tested compounds, 12b was emerged as the most active one on
LPS-induced NO production assay. Accordingly, 12b was chosen

4416
C. Zhong et al. / Bioorg. Med. Chem. Lett. 23 (2013) 4413–4418
R1
R1
OMe
OMe
COOH
O
OMe
OMe
OMe
MeO
MeO
Ph
iii
ii
i
OMe
OMe
O
O
O
MeO
OMe
P
Ph
R1
MeO
OMe
OMe
OMe
O
6a-c
9
11a-c
10
R1
1
6a
6b
6c
: R =OMe
R1
1
: R =H
1
: R =F
7a: R1=R2=OMe
OMe
OMe
7b: R1=R2=H
v
OMe
iv
1
2
7c
7d
7e
: R =H, R =OMe
*
1
2
SH
MeO
: R =OMe, R =H
*
*
R2
: R =OMe, R =CH3
1
2
MeO
S
OMe
OMe
7f: R1=OMe, R2=F
OH
7g: R1=OMe, R2=Cl
12a-c
1
R2
12a
12b
12 : R =F
: R =OMe
13a-f
1
: R =H
1
c
13a: R1=R2=OMe
R1
R1
13b: R1=R2=H
1
2
13c
13d
13e
: R =H, R =OMe
1
2
: R =OMe, R =H
OMe
OMe
OMe
OMe
1
2
vi
: R =OMe, R =CH3
vii
13f: R1=OMe, R2=F
13g: R1=OMe, R2=Cl
*
MeO
MeO
1
2
14a
14b
14c
: R =R =OMe
OMe
R2
OMe
R2
*
1
2
: R =R =H
HO
1
2
: R =H, R =OMe
14d: R1=OMe, R2=H
14e: R1=OMe, R2=CH3
7a-f
14a-f
1
2
14f
14g
: R =OMe, R =F
: R =OMe, R =Cl
1
2
Scheme 1. Synthesis of resveratrol dimerized derivatives. Reagents and conditions: (i) LiN reagent, THF, 0 °C; (ii) (CH3)3COK, toluene; (iii) BF3ꢀEt2O, 25 °C, 40 h; (iv) NaBH4,
THF, CH3OH, 25 °C, 30 min; (v) p-CH3O-PhCH2SH, In(OTf)3, CH2Cl2, 25 °C, 1.5 h; (vi) (a) mCPBA, NaHCO3, CH2Cl2, 0–25 °C, 25 min, (b) KOH, CCl4/t-BuOH/H2O = 5/5/1, 80 °C,
12 h; (vii) (a) BH3ꢀTHF, THF, 25 °C, 18 h, (b) NaOH, 30% H2O2, Na2SO3, 25–0 °C.
by ELISA. As shown in Figure 3C, the LPS stimulation could signif-
icantly increase IL-1b release in RAW 264.7 cells. However, the IL-
1b release in LPS-stimulated RAW 264.7 cells was suppressed by
co-treatment with 12b in a concentration-dependently manner.
These results further confirmed the anti-inflammatory effect of
12b.
In RAW 264.7 cells, the rapid activation of MAPK in response to
LPS has been well documented and played an important role in the
regulation with the expression of inflammatory mediators.26 To
investigate whether the anti-inflammatory response by 12b was
mediated by the inhibition of MAPK signaling pathway, the effects
of 12b on the LPS-induced phosphorylation of p38 MAPK, JNK1/2
Figure 3. Compound 12b inhibited LPS-induced inflammatory response in RAW 264.7 cells, After 12b (5–20 lM) pretreatment, RAW 264.7 cells were stimulated with LPS
(1 lg/mL) for 24 h. Western blot analysis for iNOS expression, nitrite and nitrate assay for NO production, and ELISA for IL-1b release were carried out. (A) Quantitative
analysis of iNOS expression, b-actin was used as loading control; (B) quantitative analysis of NO production; (C) quantitative analysis of IL-1b release; #P <0.05 compared with
unstimulated cells, ⁄P <0.05 compared with LPS-stimulated cells; data were from at least three independent experiments, each performed in duplicate.

C. Zhong et al. / Bioorg. Med. Chem. Lett. 23 (2013) 4413–4418
4417
Figure 4. Compound 12b suppressed LPS-induced activation of MAPK signaling pathway in RAW 264.7 cells, After 12b (5–20
lM) pretreatment, RAW 264.7 cells were
stimulated with LPS (1 lg/mL) for 45 min. The total and phosphorylation levels of MAPK were detected by Western blot. (A) Showing the total and phosphorylation levels of
MAPK detected by Western blot; (B) quantitative analysis of p-p38. Total p38 was used as loading control; (C) quantitative analysis of p-JNK1/2. Total JNK1/2 was used as
loading control; (D) quantitative analysis of p-ERK1/2. Total ERK1/2 was used as loading control; #P <0.05 compared with unstimulated cells, ⁄P <0.05 compared with LPS-
stimulated cells; data were from at least three independent experiments, each performed in duplicate.
Figure 5. Compound 12b suppressed LPS-induced inflammatory responses through inhibition of p38 MAPK and JNK1/2 signaling pathway, After preincubation with 12b
(20 lM), SB203580 (p38 inhibitor, 10 lM), SP60012 (JNK1/2 inhibitor, 10 lM), or PD98059 (ERK1/2 inhibitor, 10 lM), RAW 264.7 cells were stimulated with LPS (1 lg/mL)
for 24 h. Western blot analysis for iNOS expression, nitrite and nitrate assay for NO production, and ELISA for IL-1b release were carried out. (A) Quantitative analysis of iNOS
expression. b-Actin was used as loading control; (B) quantitative analysis of NO production; (C) quantitative analysis of IL-1b release; #P <0.05 compared with unstimulated
cells, ⁄P <0.05 compared with LPS-stimulated cells; data were from at least three independent experiments, each performed in duplicate.
and ERK1/2 were examined in RAW 264.7 cells. LPS could cause a
significant phosphorylation of MAPK (p38 MAPK, JNK1/2 and
ERK1/2) after stimulation for 45 min detected by Western blot
analysis (Fig. 4). Compound 12b concentration-dependently
diminished LPS-induced phosphorylation of p38 MAPK (Fig. 4B)
and JNK1/2 (Fig. 4C). However, it had a little effect on phosphory-
lation of ERK1/2 (Fig. 4D). These results strongly suggested that
inhibition of p38 MAPK and JNK1/2 phosphorylation by 12b may
be responsible for achieving LPS-induced inflammatory response.
To further verify that anti-inflammatory effect of 12b was
mediated through inhibition of p38 MAPK and JNK1/2 signaling
pathway, RAW 264.7 cells were preincubated with 12b (20
SB203580 (p38 inhibitor, 10 M), SP60012 (JNK1/2 inhibitor,
10 M), or PD98059 (ERK1/2 inhibitor, 10 M). The LPS
lM),
l
l
l

4418
C. Zhong et al. / Bioorg. Med. Chem. Lett. 23 (2013) 4413–4418
16. Silva, A. A.; Haraguchi, S. K.; Cellet, T. S. P.; Schuquel, I. T. A.; Sarragiotto, M. H.;
Vidotti, G. J.; de Melo, J. O.; Bersani-Amado, C. A.; Zanoli, K.; Nakamura, C. V.
Nat. Prod. Res. 2012, 26, 865.
17. Wang, S. G.; Ma, D. Y.; Hu, C. Q. J. Asian Nat. Prod. Res. 2004, 6, 241.
18. Zhong, C.; Zhu, J.; Chang, J.; Sun, X. Tetrahedron Lett. 2011, 52, 2815.
19. Zhu, J.; Zhong, C.; Lu, H. F.; Li, G. Y.; Sun, X. Synlett 2008, 458.
20. Sun, X.; Zhu, J.; Zhong, C.; Izumi, K. J.; Zhang, C. Chin. J. Chem. 2007, 25, 1866.
21. Zhong, C.; Liu, X.-H.; Hao, X.-D.; Chang, J.; Sun, X. Eur. J. Med. Chem. 2013, 62,
187.
stimulation induced a markable increase in the expression of iNOS
and release of NO and IL-1b compared with unstimulated cells. Co-
treatment with 12b (20 lM) significantly reduced the expression
of iNOS and release of NO and IL-1b in LPS-stimulated cells
(Fig. 5). In addition, the effect of 12b on LPS-induced inflammatory
responses was mimicked by SB203580 (p38 inhibitor) or SP60012
(JNK1/2 inhibitor), but not PD98059 (ERK1/2 inhibitor) (Fig. 5).
Overall, the results further confirmed that 12b suppressed LPS-
induced inflammatory responses through inhibition of p38 MAPK
and JNK1/2, but not ERK1/2 signaling pathway.
In conclusion, four-types (types I–IV) of resveratrol dimerized
analogues were synthesized and evaluated for anti-inflammatory
activity. In general, analogues in both types I and IV were more po-
tent than other two types. Among these, the methylated precursors
(e.g., 6b, 6c, 7a, and 12b) were found to be more effective than
their corresponding natural products (e.g., 2a, 3a, 4a). Of the com-
pounds synthesized, compound 12b could significantly suppress
LPS-induced iNOS expression and NO production through p38
MAPK and JNK1/2 signaling pathways. Accordingly, our findings
provide a partial description of the mechanism underlying the
anti-inflammatory effect of 12b. It is believed that this compound
can be a good lead for further design of iNOS inhibitors.
22. Zhang, F.; Liu, J.; Shi, J. S. Eur. J. Pharmacol. 2010, 636, 1.
23. Gautam, R.; Jachak, S. M. Med. Res. Rev. 2009, 29, 767.
24. Typical procedures for the synthesis of derivatives of type I. Preparation of 1,2-
bis(3,5-dimethoxyphenyl)ethane-1,2-dione (10): To a solution of naphthalene
(23.3 g, 181 mmol) in anhydrous THF (100 mL) under nitrogen was added
lithium (1.26 g, 181 mmol) at room temperature for 8 h. The mixture was add
dropwise to a solution of 3,5-dimethoxybenzoic acid 9 (15.0 g, 82.3 mmol) in
anhydrous THF (300 mL) at 0 °C and quenched with water when dropping
complete. The reaction mixture was concentrated. Then the organic layer was
separated and the aqueous layer was extracted with ethyl acetate (3 ꢁ 30 mL).
The combined organic extracts were washed with brine (30 mL), dried over
anhydrous sodium sulfate, filtered, and concentrated in vacuo. The residue was
recrystallized in ethyl acetate to give 10 as a yellow sold (12.0 g, 44%).
Preparation of 1,2-bis(3,5-dimethoxyphenyl)-3-phenylprop-2-en-1-one (11b): To
a solution of 10 (1.00 g, 3.03 mmol) and benzyl-diphenyl-phosphate oxygen
(0.89 g, 3.03 mmol) in anhydrous THF (100 mL) under nitrogen was added
potassium tert-butoxide (0.56 g, 4.54 mmol) at room temperature for 1 h. The
reaction mixture was concentrated. Then the organic layer was separated and
the aqueous layer was extracted with CH2Cl2 (3 ꢁ 20 mL). The combined
organic extracts were washed with brine (30 mL), dried over anhydrous
sodium sulfate, filtered, and concentrated in vacuo to afford the liquid which
was purified by silica gel chromatography, utilizing ethyl acetate and hexane
(1:10) as mobile phase, to afford 11b as a yellow oil (0.87 g, 71%).
Acknowledgements
Preparation
of
trans-2-(3,5-dimethoxyphenyl)-4,6-dimethoxy-3-phenyl-2,3-
Financial support by the National Natural Science Foundation of
China (No: 30973612), Shanghai Municipal Committee of Science
and Technology (No: 10431903100) and National Basic Research
Program of China (973 Program, No: 2010CB912603) are
acknowledged.
dihydroinden-1-one (6b): To a solution of chalcones 11b (0.40 g, 1.00 mmol)
in CH2Cl2 (15 mL) was added dropwise BF3ꢀOEt2 (0.12 mL, 1.00 mmol) via
syringe. After the reaction mixture was stirred at room temperature for 40 h
under a nitrogen atmosphere, the reaction was quenched by the addition of
H2O (5 mL). The resulting mixture was extracted with CH2Cl2 (3 ꢁ 10 mL). The
combined organic phases were washed with brine and dried over anhydrous
Na2SO4. After removal of solvent, the resulting yellow residue was
recrystallized in methanol to afford 6b as a white solid (0.38 g, 94%).
References and notes
Preparation
of
trans-2-(3,5-dimethoxyphenyl)-4,6-dimethoxy-3-phenyl-2,3-
dihydro-1H-inden-1-ol (12b): To a solution of 6b (0.40 g, 1.00 mmol) in THF
(10 mL) was added NaBH4 (0.23 g, 6.00 mmol) at room temperature. Then the
reaction mixture was added methanol (10 mL) and continuously stirred at
room temperature for 30 min. Upon completion, the reaction mixture was
concentrated. After separated the organic layer, the aqueous layer was
extracted with CH2Cl2 (3 ꢁ 10 mL). The combined organic extracts were
washed with brine (15 mL), dried over Na2SO4, filtered, and evaporated in
vacuo to give 12b (0.40 g, 99%). 1H NMR (CDCl3, 400 MHz) d: 3.17 (t, J = 6.8 Hz,
1H), 3.53 (s, 3H), 3.73 (s, 6H), 3.86 (s, 3H), 4.30 (d, J = 7.0 Hz, 1H), 5.20 (d,
J = 6.3 Hz, 1H), 6.33 (d, J = 9.8 Hz, 3H), 6.42 (s, 1H), 6.66 (s, 1H), 7.02–7.06 (m,
2H), 7.13–7.25 (m, 3H); 13C NMR (CDCl3,100 MHz) d: 54.12, 55.21, 55.26, 55.57,
67.36, 82.18, 98.57, 99.31, 99.71, 105.84, 123.08, 125.92, 127.34, 127.96,
144.11, 144.21, 157.05, 160.77, 160.86, 161.63; ESI-MS m/z: 389.2 [MꢂH2O]+;
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IR (KBr) m .
max = 3441, 2935, 2836, 1596, 1511, 1455, 1203, 1148 cmꢂ1
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